RO vs RO/DI? Need help deciding.

[MamaLovesHerReefTank]

Is there a big difference in the water quality between ro and ro/di? Looking into purchasing a unit but also trying to keep costs realistic. Thanks.

 

[Crabs McJones]

Is there a big difference in the water quality between ro and ro/di? Looking into purchasing a unit but also trying to keep costs realistic. Thanks.

Absolutely :) Depended on your source water most RO membranes have a 99% rejection rate, which means some TDS is going to make its way through. DI is that nice little polish at the end that brings you down to 0 TDS which means there are absolutely no dissoved solids in your water.

 

[Denisk]

Definitely get an Rodi unit. You’ll never look back or question the decision you made.

 

[iced98lx]

Is there a big difference in the water quality between ro and ro/di? Looking into purchasing a unit but also trying to keep costs realistic. Thanks.

Most people who run RO only think of it like this:

If I use only RO, and the water is 2TDS (which means 2 parts per million of total dissolved solids) that seems pretty low if I started with 300.

Which is accurate but the issue lies in what those 2 ppm of solids are.

Someone may be able to have a VERY successful reef tank with 10tds water because the solids left over are something that doesn't impact their tank. Others will note obvious algae blooms when their DI resin is exhausted signaling whatever is left after the RO isn't something they want in their tank.

Start with good water so you're not chasing ghosts later in your tank's life.

 

[chipmunkofdoom2]

What @crabs_mcjones said.

Elements like copper, phosphates, ammonia (as ammonium) and silicates all are handled by the DI resin. These are all elements that are particularly problematic for reef tanks, and the only real way to get rid of them is with deionizing resin. Even if the final product water TDS after the membrane is very low, it could be very high in elements that are very dangerous for reef tanks.

I'm a self-proclaimed cheapskate. I'll never have an issue with reefers looking to save money. However, water quality is not the place to do it. This hobby is more about keeping clean water than it is keeping corals or fish.

 

[MamaLovesHerReefTank]

What @crabs_mcjones said.

Elements like copper, phosphates, ammonia (as ammonium) and silicates all are handled by the DI resin. These are all elements that are particularly problematic for reef tanks, and the only real way to get rid of them is with deionizing resin. Even if the final product water TDS after the membrane is very low, it could be very high in elements that are very dangerous for reef tanks.

I'm a self-proclaimed cheapskate. I'll never have an issue with reefers looking to save money. However, water quality is not the place to do it. This hobby is more about keeping clean water than it is keeping corals or fish.

So basically, if I'm battling high phosphates, which I am, I need the di because just ro doesn't remove them? Thank you for this. Now I know why I need the di in easy to understand reasoning.

 

[MamaLovesHerReefTank]

So basically, if I'm battling high phosphates, which I am, I need the di because just ro doesn't remove them? Thank you for this. Now I know why I need the di in easy to understand reasoning.

What does the gpd mean? Lower gpd, takes more time to produce water?

 

[Crabs McJones]

What does the gpd mean? Lower gpd, takes more time to produce water?

GPD stands for Gallons Per Day. It's how much water you're able to produce with your RO system in a 24 hour time period.

 

[MamaLovesHerReefTank]

GPD stands for Gallons Per Day. It's how much water you're able to produce with your RO system in a 24 hour time period.

Thank you. So if I do a 20g water change, ro/di unit with 50gpd should be fine? Can water be made a couple days ahead like I do now?

 

[chipmunkofdoom2]

Thank you. So if I do a 20g water change, ro/di unit with 50gpd should be fine? Can water be made a couple days ahead like I do now?

Yes, that's what most reefers do. Most use a large reservoir and have the unit make water ahead of time. A 50 GPD membrane would certainly work if you had sufficient lead time. It's worth noting that the parts on most RO/DI systems are interchangeable. You should be able to buy a 75GPD membrane unit for about the same price as a 50GPD unit. The only difference between these two will likely be the membrane inside the membrane housing (and maybe the flow restrictor). Everything else will probably be the same.

 

[K. Steven]

As an example of why RODI is superior to RO, I just moved 2.5 miles from my previous apartment and into a different city. Before, I had 1 ppm TDS after RO, then zero after DI. Now, I have 18 ppm TDS after RO and zero after DI. The DI stage makes all the difference. Bad water gives you bad results right off the bat. Don't start behind the 8 ball before even getting the tank up and running.

 

[XNavyDiver]

Just chiming in, I agree with the others who say RODI. As a matter of fact, I just expanded my DI by installing a brs 3 canister expansion retro fit to my current RODI system. As it's been said before; we're water farmers.

 

[Crabs McJones]

Thank you. So if I do a 20g water change, ro/di unit with 50gpd should be fine? Can water be made a couple days ahead like I do now?

Yup! So on average your RO unit should be producing about 2 gallons of product water per hour. And you can store it in your container until you need it :)

 

[JoshH]

I'd keep an eye on the rejection rate of whichever RO membrane you decide to get, most are around the 92-96% range. Get the best one you can, this will help extend the life of your DI Resin. 50GPD is plenty for your setup and if you store your water in an airtight container the amount of contaminants the water will absorb will be kept to a minimum.

 

[Crabs McJones]

Just chiming in, I agree with the others who say RODI. As a matter of fact, I just expanded my DI by installing a brs 3 canister expansion retro fit to my current RODI system. As it's been said before; we're water farmers.

Same here @XNavyDiver I was using a single stage DI canister, and recently upgraded it to dual stage. I got the 150GPD upgrade kit from BRS and it was recommended to double up on my DI

 

[XNavyDiver]

Same here @XNavyDiver I was using a single stage DI canister, and recently upgraded it to dual stage. I got the 150GPD upgrade kit from BRS and it was recommended to double up on my DI

Mine was a duel stage DI (with the two small tubes mounted on top of the whole unit), but I wasn't satisfied with amount of DI resin it was able to hold, so I went ahead and got that big 3 stage and bypassed the old two stage that came with the unit. Filled the first with cation, second with anion and the last with mixed bed.

 

[Crabs McJones]

Mine was a duel stage DI (with the two small tubes mounted on top of the whole unit), but I wasn't satisfied with amount of DI resin it was able to hold, so I went ahead and got that big 3 stage and bypassed the old two stage that came with the unit. Filled the first with cation, second with anion and the last with mixed bed.

Nice! I eventually want to do the same setup. But don't have anymore room under my kitchen sink ;Hilarious Right now its just two mixed bed canisters

 

[MamaLovesHerReefTank]

Since I am in Canada, availability and cost become a bit of a factor. I was looking at this on amazon. https://www.amazon.ca/Aquatic-Chang...0095331&sr=8-1&keywords=aquaticlife+ro+buddie Would this be good to use or am I at the lowest level of filtering with this.

 

[XNavyDiver]

Nice! I eventually want to do the same setup. But don't have anymore room under my kitchen sink ;Hilarious Right now its just two mixed bed canisters

I don't think there is an under sink cabinet large enough to contain my system. Six large canisters all lined up mounted to a wall in my garage! I looks ridiculous.

 

[Crabs McJones]

Since I am in Canada, availability and cost become a bit of a factor. I was looking at this on amazon. https://www.amazon.ca/Aquatic-Chang...0095331&sr=8-1&keywords=aquaticlife+ro+buddie Would this be good to use or am I at the lowest level of filtering with this.

Alot of reefers have had good luck with that unit. The only thing to make sure is that you mount it vertically and not horizontally. What happens if you mount it horizontally is the water can channel in the DI chamber as the resin starts to deplete, and therefore doesn't get forced through the rest resin, and you'll start to get TDS creeping through while most of the resin is still good. If you force it to raise up through the resin from bottom to top, it doesn't get the opportunity to channel and pass through.